FIG. 1 shows a conventional brake hose. The conventional brake hose 20 is composed of an inner tube rubber layer 1 that has a hose hole 1A formed inside to be filled with brake fluid and that is of ethylene-propylene-diene rubber, a first braided fiber reinforcing layer 2 that is formed on the periphery of the inner tube rubber layer 1 and that is made braiding fibers of high tenacity rayon, polyester fibers, nylon fibers, alamido fibers etc., a second braided fiber reinforcing layer 9 that is formed through a middle rubber layer 8 of natural rubber on the periphery of the first braided fiber reinforcing layer 2, and an outer tube rubber layer 5 that is formed on the periphery of the second braided fiber reinforcing layer 9 and that is of chloroprene rubber etc.
The reason why the middle rubber layer 8 is provided is that it prevents the rubbing between fibers of the first braided fiber reinforcing layer 2 and the second braided fiber reinforcing layer 9 so as to enhance the durability. In case of not having the middle rubber layer 8, the hose may be broken since the braided fibers are abraded by rubbing each other due to the pressuring, bending or meandering motion generated during using it so that the strength of fibers lowers.
There is also provided an adhesive layer between the second braided fiber reinforcing layer 9 and the outer tube rubber layer 5 to satisfy the performance required in various standards, such as JIS D2601 “automobile parts/non-mineral oil series fluid brake hose assembly” and, especially, to enhance the sealing performance between hose and fitting to satisfy “brake fluid suitability”.
Furthermore, according to the standards of JIS D2601, it is regulated that a vehicle brake hose has more than two fiber layers.
The vehicle brake hose is subjected to various limitations described above and, in recent years, it is desired that the weight of brake hose is reduced to lower the manufacturing cost and to advance environment measures.
However, in the conventional brake hose, when the amount of material used is simply reduced so as to reduce the weight of brake hose and to lower the manufacturing cost, the performance, especially durability, regulated by the JIS standards could not be maintained.
Also, when the amount of material used is reduced, the amount of hose expansion that highly influences the braking force and brake feeling could be increased.
On the other hand, in the layout designing of brake hose when developing the vehicle, the brake hose is disposed in a narrow and tight region because of the enlarging of engine room, the enhancement of suspension performance and braking force etc. Therefore, it is desired that the rigidity of brake hose is reduced to facilitate the installation of brake hose.